Recently, neurological stimulation has received increased interest as a medical tool for providing electrostimulation of brain tissue, especially deep brain tissue, in an effort to provide therapeutic benefit for patients suffering from various brain disorders. Such neurological stimulation has been used, for example, to control epileptic seizures and tremors associated with Parkinson and other brain diseases. Generally such medical systems include an implantable pulse generator (i.e., pacemaker), an elongated body with electrodes on the distal end which is implanted in the brain (typically in the region of the thalamus), and a connector on the proximal end to electrically connect the electrodes to the pacemaker.
The current implant procedures are performed in a surgical setting using stereo tactic techniques. The target area within the brain is generally identified using, for example, magnetic resonance imaging, computer tomography, or ventriculography. Once the implantable device is advanced to the target area, electrical stimulation tests are conducted to confirm the ideal site for embedding the electrode and for determining the pacing parameters suitable for good tremor suppression. In some cases, two implantable devices, each with its own pacing parameters, are implanted for bilateral stimulation of the thalamus region to control bilateral tremors.
Placement of the electrodes within the brain is generally not as precise as desired. Since the electrodes may not be placed properly, the desired tremor control may not be affected. In that case, the implant device and its electrodes may need to be relocated, thereby subjecting the brain tissue to increased risk of damage. To at least partially remedy this situation, four electrodes, each formed by a metal band surrounding the entire circumference of the device, have been used. Any combination of the four electrodes can be used for electrical stimulation by using any one electrode to deliver the electrical pulse and any other of the remaining electrodes to provide the return path. Using appropriate software, the pacemaker can be switchable and programable so that the appropriate combination of electrodes can be used. Using such systems, the pacing current or voltage is applied to, and absorbed by, tissue surrounding the electrode throughout the entire 360° circumference. Although this present system does allow control through the selection of the two electrodes (out of the four electrodes available) to form the pacing circuit, further control and precision with regard to electrode placement relative to the tissue to be treated would be desirable. Moreover, this arrangement does not allow directional electrostimulation.
Medical implant devices are also used for electrostimulation and/or monitoring of other tissue, including, for example, tissue and/or viscera of the gastrointestinal tract. It is well known that more than 70% of illnesses affecting the digestive tract are of a functional nature. Today such illnesses are treated predominantly using pharmacological means. Since drugs generally have side effects, particularly when the drugs cure the symptom and not the underlying problem or dysfunction, they must often be administered temporally. Indeed, if the side effects are sufficiently serious, the drug may have to be discontinued before full benefit to the patient is realized; in many cases the underlying illness remains.
The important role played by electrophysiology in controlling gastrointestinal activity has become increasingly apparent in recent years. Thus, the possibility exists of correcting dysfunction by means of electrostimulation applied at specific frequencies, sites, and modalities and with regard to the self-regulating electromotor physiology of the gastrointestinal organs or tract. It has recently been shown, for example, that changes occur in the motility and electromotor conduct of the gastric tract in eating disorders (e.g., obesity, thinness, bulimia, anorexia). Disturbances in electromotor activity in diabetic gastroparesis, reflux in the upper digestive tract, and numerous other gastroenterological functional pathologies have also been observed.
Stimulation of the intrinsic nervous system of the stomach is likely to have two major consequences or effects: (1) the correction and direct control of the electromotor activity of the intestines and (2) the stimulation of increased incretion of specific substances (i.e., gastroenteric neuromediators) produced by the intrinsic nervous system. Curing of functional illnesses involving the digestive system and, more broadly, involving disorders in any way connected to, or associated with, the digestive system is, therefore, closely linked to the progress of research in the field of electrophysiology.
An indispensable condition for modifying the electrical activity of the digestive system's intestinal tract and related neurohormonal incretions is the use of an implant system to generate electrical impulses (electrical stimuli) and means (e.g., electrocatheters) to connect them to the viscera and/or intestines to be stimulated. These treatment methods involve an “invasive” surgical technique to implant the electrocatheter in the abdomen. This may involve open or, preferably, micro-invasive surgery (i.e., video-laparoscopic surgery). Current electrocatheters to stimulate electrically and/or monitor endo-abdominal viscera may have metal microbarbs which are angled in such a way as to permit application of the end of the catheter and to prevent it subsequently from being dislodged. However, metal microbarbs can damage surrounding tissue especially when exposed to the vigorous action of the digestive tissue and/or organs. Among the undesirable consequences of such damage is erosion of the electrode into the lumen of the gastrointestinal tract. This would result in contamination of the abdominal cavity and the electrode. The subsequent infection would, at a minimum, require removal of the catheter and involve an additional operation.
During laparoscopic procedures, after administering a general anesthetic, the patient's abdomen is inflated with CO2 or another inert inflammable gas, thereby transforming the abdominal cavity from a virtual to a real cavity. Rigid tubes with air-tight valve mechanisms (“trocars”) are then inserted into the gas-filled abdominal cavity so that a video camera and other surgical instruments can be introduced into the abdomen. The operation then proceeds by viewing the video images transmitted by the camera. Multiple trocars are required. Generally, the first trocar provides access to the abdomen by the video camera in order to monitor the surgical procedure. A clamp is normally inserted in the second trocar to move or retain the hepatic edge that normally covers the lesser curve of the stomach or other viscera depending on the type of operation to be performed. A third trocar provides access for a maneuvering clamp or laparoscopic forceps. The fourth trocar is used for the introduction of instruments as well as the electrocatheter to be implanted in the stomach wall of the patient. The structure of the electrocatheter plays an important part in facilitating the specific operation for whichever of the patient's organs and/or viscera the surgeon aims to stimulate.
Each of the trocars used, of course, requires a separate tract through the skin and abdominal wall. To keep the abdomen inflated, valves are used with the trocars to provide a gas-tight seal. Introduction of a medical device, such as an electrocatheter or implantable electrode, into the abdomen generally requires the use of laparoscopic forceps to grasp the device. Such devices, which are generally inherently fragile in nature, could be damaged if grasped too firmly by the forceps. Thus, for example in the case of an electrocatheter having electrode leads, the interior conductor wires could be broken, rendering the device dysfunctional or completely useless.
It Would be desirable, therefore, to provide an improved implant device which can be easily and precisely positioned for attachment to the target tissue or organ and which can be controlled in place to provide the electrical path through the anode and cathode to provide improved electrostimulation and/or monitoring for the tissue of interest. It would also be desirable to provide an improved implant device with a plurality of micro-electrodes which allows variable electrical pathways such that improved electrical stimulation and/or monitoring of the target tissue or organ can be achieved. It would also be desirable to provide an improved implant device wherein the electrical path can be modified as needed to take into account shifting or movement of the implant device over time in order to maintain the desired electrostimulation and/or monitoring of the tissue of interest. The present invention provides such implant devices. The present implant devices allow precise placement of the electrode leads relative to the tissue to be treated. The present implant devices provide flexibility with regard to electrostimulation of the tissue to be treated. Moreover, the present implant devices provide flexibility to modify the electrical path through the electrodes to allow for precise electrostimulation of the tissue to be treated both at the time of implantation and at later times wherein the optimum location for electrostimulation may be changed due to movement of the implant device itself or due to the changing medical condition of the patient. Moreover, the present implant devices provide flexibility and accuracy by allowing directional sensing and/or directional stimulation of tissue (including for example, brain tissue). The present implant device would be especially useful, for example, for treatment of neurological conditions in the brain (as well as other neurological tissue such as spinal tissue). The present implant devices are also useful, for example, for electrostimulation and/or monitoring of tissue and/or organs of the gastrointestinal tract.